Hoisting apparatus



D. A. WALLACE HOISTING APPARATUS Sept. 29, 1953 3 Sheets-Sheet 1 FiledMarch 19, 1948 INVENTOR. jay 1i M aZ/azce ITTORA/IX Sept. 29, 1953 D. A.WALLACE HOISTING APPARATUS 5 Sheets-Sheet 2 Filed March 19, 1948 3Sheets-Sheet 5 D. A. WALLACE HOISTING APPARATUS Q\ Tl: l' I q l hh'l lllM l l l l I l l II I .l l l I i J I .I: I. ll I I II'IHHI FWK Sept. 29,1953 Filed March 19, 1948 Patented Sept. 29, 1953 HOISTING APPARATUSDavid A. Wallace, Grosse Pointe Farms, Mich.,

assignor to Walco, Inc., Detroit, Mich., a corporation of MichiganApplication March 19, 1948, Serial No. 15,827

12 Claims.

This invention relates to hoisting apparatus and is an improvement inhoisting apparatus of the character shown in my patent applicationsSerial Nos. 653,385, 711,649 and 775,191 filed March 9, 1948; November22, 1946 and September 20, 1947, respectively, now Patents Nos.2,576,907, 2,576,153 and 2,576,908, respectively, dated November 27,1951. Attention is also directed to my related copending applicationswhich have issued as Patents Nos. 2,598,200 and 2,598,625 of May 27,1952.

More specifically the invention relates to improvements in hoistingapparatus which is particularly adapted for hoisting vehicles.

One of the main objects of the invention is to provide in hoistingapparatus having a plurality of independently and simultaneouslyoperable hoisting units, a power driving mechanism which can beoperatively engaged with one, all or a selected number of the hoistingunits to positively elevate and positively lower the boom membersthereof and which positively locks the hoisting units against unintendedlowering from fully or partially raised positions.

Another object of the invention is to provide power driving mechanism inhoisting apparatus of this kind in which a single screw member serves toactuate all the hoisting units in their raising and lowering operations.

Another object of the invention is to provide improved reduction gearmechanism for driving a screw of this kind which accommodates extremelylow positioning of the screw.

A further object of the invention is to provide driving mechanism forhoisting apparatus of this kind which can be conveniently controlled toraise and lower a load by any reversible prime mover,- such as a simplereversing electric motor.

A still further object of the invention is to provide mechanism forselectively coupling the boom members of the respective hoisting unitsto their common actuating screw.

Additional objects of the invention are to provide relatively shiftablymounted hoisting units in apparatus of this kind which can beconveniently variably spaced to accommodate loads of diiierent lengths,to provide relatively shiftable hoisting units which can be shifted withrespect to each other by the same driving mechanism that is utilized topositively raise and lower the boom members of the units, to provideimproved and conveniently manipulatable means for releasably holding therelatively shiftable hoisting units in a selected position, and toprovide improved means for presetting the hoisting units for receivingspaced portions of a number of vehicles of difierent lengths andconstructions in advance of placement of the vehicles upon the hoistingapparatus.

Another object of the invention is to provide mechanism forautomatically interrupting operation of the power driving mechanism whenthe boom members of the hoisting units reach predetermined upper andlower positions respectively.

A further object of the invention is to provide screw operated hoistingapparatus which moves a load upwardly and downwardly in a path whichdoes not excessively depart from a vertical course or require but alimited space at the opposite ends of the load to accommodate swingingthereof during the lifting and lowering operations.

Another object of the invention is to provide a system of levers inscrew operated hoisting apparatus of this kind which does not require anexcessively large starting torque in order to produce the initial loadlifting action.

A further object of the invention is to provide screw operated hoistingapparatus of this kind which, when in its lower position, does not haveits parts extending excessively above the floor level or base structureon which it is mounted or otherwise projecting into obstructingpositions.

Another object of the invention is to provide improved hoistingapparatus of this character which can be disposed in a groove in a floorof relatively shallow depth or upon a fioor without requiring deep pitsfor its accommodation.

An illustrative embodiment of the invention is shown in the accompanyingdrawings, in which:

Fig. l is a perspective view showing hoisting apparatus embodying theinvention in its elevated position.

Fig. 2 is a fragmentary, end elevational View illustrating one manner inwhich the base structure of the hoisting apparatus may be installed toaccommodate the driving of a vehicle into position to be lifted.

Fig. 3 is a fragmentary side elevational view of one of the hoistingunits of the apparatus, illustrating in dotted lines various positionsof the boom member of the unit during its lifting action.

Fig. 4 is a plan view of substantially the left half of the hoistingapparatus shown in Fig. 1, illustrating the left hoisting unit in itslowered position.

Fig. 5 is a plan view or substantially the right half of the hoistingapparatus shown in Fig. 1, illustrating the right hoisting unit in itslowered position.

Fig. 6 is a transverse sectional view taken on line 6-6 of Fig. 4.

Fig. '7 is a transverse sectional view taken on line 1-1 of Fig. 4.

Fig. 81s a side elevational view of the portion of the hoistingapparatus shown in Fig. 4, showing one "side rail thereof broken awayand illustrating in dotted lines the raised position of the boom memberof the hoisting unit.

Fig. 9 is a schematic wire diagram of an electrical control circuit fora hoist embodying the invention.

Fig. 10 is a vertical sectional view of the reduction gear mechanism ofthe driving apparatus shown in Fig. 1.

Fig. 11 is a side elevational view of a tool by which the hoisting unitsmay be preset in position for receiving a vehicle of known length.

1 of the drawings is illustrated'hoisting apparatus embodying theinvention which comprises hoisting units A and B each of which aresubstantially identical, the description of one of which will serve, inall but certain respects hereinafter specified, for the others. Thesehoisting iirii'ts are particularly constructed to lift vehicles but maybe readily adapted to the lifting of numerous other articles. 'Ihey arepreferably operatively mounted on a track comprising spaced rails f andH of channel-shaped cross section having'lnwardly facing upper flangesl2 and I3 'andlower flanges and I5. The rails l0 and H may be mountedina shallow groove formed in aplatform'str'ucture I6, illustrated in Fig.2 which'is disposed upon a floor structure or they may be mounted in ashallow groove (not shown) of a floor structure with the upper flangesI2 and I3 flush with thefloorsurface.

:The hoisting units'A and B each includes a shiftable carriage,'generally designated by the numeral I'Lhaving a horizontal base plate18 and 'a lvertically upstanding flange l9. Provided on each of theopposite ends of the shiftable carriage are shoes20 and2| slidablymounted bet ween the flanges l2 and Hand the flanges nand l of the railslfl'and rsepectively. 'The shoes'20 and 2| have recesses 22 and 23,respectively formed in their outer extremities for reducing "the areasof contact between the ex- "tremities of the shoes and the web portionsof thera'ils l0 and I. An outer corner portion of the shoe ls'cut awayto provide a passage 24' for accommodating an electrical wire I03,herelnal'ter referred to. The carriage l'i' includes "spaced flanges 21'and 28 disposed between and substantially parallel to the shoes and 2|and which are preferably formed integral with or welded to the baseplate l8'a'nd upstanding flange l9, as illustrated in Fig. 4.

Each'hoisting 'unit'includes a boom member, generally designated by thenumeral 29, which coinpri's'es'a pair of channel members 30 and 3|,

4 end 3| of the channel member 3| is received etween the shoe 28 andflange 28 of the carriage I! and is pivotally secured thereto by a pin34, having a retaining collar 35 and which is received in aperturesformed in the shoe 20 and flange 28 of the carriage IT, as shown in Fig.7.

A load receiving seat, generally designated by the numeral 35 ispivotally mounted on the upper ends of the channel members '30 and 3|,as illustrated in Figs. 1 and 3. The load receiving seat 36 comprises abar 31 having upwardly extending notched flanges 38 provided on itsopposite extremities for receiving a vehicle axle or other portion of aload to be lifted. Provided on the opposite side of the bar 31 arespaced downwardly extending ears 39 for receiving pins When the boommember comprising the channel members 39 and 3| is in its uppermostposition, the lower side of the bar 31 seats upon the upper extremitiesof the channel members. During movement of the boom member 29 from itslower to its upper position the seat 36 is retained in a substantiallyhorizontal position by parallelogram mechanism including link members"41 extending substantially parallel to the channel members 39 and 3|which are pivotally attached at their upper ends by a pin 42 to rigidarms 43 extending from the lower side of the baril of the seat member,as shown in Fig. 3. The lower ends of the links are pivotally attachedby a pin 44 carried by and extending upwardly from the base portion l8of the carriage IT. The

pivotal axes provided by the pins 42 and "44 are the boom memberprovided by the pins 82 and 34, respectively. This provides aparallelogram mechanism which retains and supports the' s'eat 36 inhorizontal load supporting position during movement of the boom member29 between; its lower and upper positions. When the boom member is inits upright position the seat 35 is supported in horizontal position byengagement of its lower side with the upper eztre'mities'of the channelmembers 33 and 3|.

The boom member 29 is supported and guided during its movement byliriks45 each of which is pivotally attached at oneend to a plate 48fixed to one channelmember respectively "of the boom. The plates 45extend upwardly from'the lower position of the boom member, asillustrated in Fig. 4. The upper end of each link' 45" is pivotallyattached toits associated plate 46 by pins 4'! and the links 45 aredisposed adjacent the facing sides of the channel members 3D"and 3|. Thelower ends of the links 45 are pivotally'attached toa cross bar 48 whichextends between the rails I3 and H of the track structure. This cross'bar'is provided with upwardly'extei'r' ding shoes 49 and 53 which areengaged between the flanges|2 and I4 of the rail Hi and the flanges i3and I5 of the rail l The upper cornerfof the shoe 49 is cut'away toaccommodate thewir'cs IN and I03. The cross bar 48 includes integralupwardly extending pairs of flanges 5| and 52 and a central bearingportion 53 having a bore v The lower end of one link is received betweenthe flanges 52 and pivotally attached thereto by a pin 55 and the lowerend of the other link 45 is received between the flanges 5| andpivotally attached thereto by a pin 56. :The cross bar 48 is preferablyreleasably fixed to the 5 side rails I8 and II by pins 51 or othersuitable means. If desired this attachment may be made by the use ofbolts or cap screws. The channel members 38 and 3| of the boom 29 areadapted to be received between the shoes 49 and 50 and the adjacentflanges SI and 52 respectively when the hoist is in its lower position.

The hoist member B is substantially identical to the hoist member A andsimilar parts are designated by the same numerals. The hoist member Bhowever, has a slightly different seat generally designated by thenumeral 36' which includes a bar 31 having a channel in its upper sidebounded by flanges 58 in which rests 59 are shiftably mounted. Each rest59 has a notch 60 in its upper side for receiving a portion of the loadto be lifted.

The lower ends of the links 45 of the hoist B are pivotally attached toa cross bar GI which differs substantially from the cross bar 48 of thehoist A. The cross bar 6| has pinion segments 82 fixed on its oppositeends and provided with teeth 63 which are adapted to mesh with the teeth65 of a rack 65 mounted on each of the lower flanges Ill and I5 of therails I and II, respectively. The lower ends of the links 55 of thehoist B are pivotally attached by a pin 86 to each of the gear segments62, respectively which are rigid with the cross bar 6|. The gearsegments 62 fit between the upper and lower flanges of the rails I8 andII with suflicient clearance to permit the segments to be lifted out ofengagement with the racks and selectively positioned in variouslocations along the racks 65. A handle 6i is provided for lifting thecross bar for this purpose. Any suitable means may be employed fordetachably securing the cross bar 6i in a plurality of selectedpositions in order to vary the spacing of the hoisting units A and B tofacilitate lifting of loads or vehicles of different lengths orconstructions.

The driving apparatus by which the boom members 28 of the hoisting unitsA and B may be selectively individually and simultaneously positivelyraised and lowered comprises a screw member, generally designated by thenumeral 68, having threads e9 thereon associated with each of the boommembers 29, respectively. The screw member 68 preferably comprises aplurality of sections which are connected together in longitudinalalignment by couplings 10. The respectively opposite end portions of thescrew member 38 are journalled in bearings provided in transverse crossmembers H and I2 which extend between and are fixed to the ends of therails is and II. One or more intermediate cross member it also extendsbetween and is fixed to intermediate portions of the rails and isprovided with bearings for rotatively supporting the screw member atlocations between its ends. The bearing 58 of the cross bar 48 alsorotatively supports an intermediate portion of the screw member.

Each carriage ll of the boom members A and 33 includes a releasable nutmember, generally designated by the numeral I4 which is adapted 'o bethreadedly engaged with the screw member in the manner hereinafter setforth. The nut member 74 comprises separable internally threadedsemi-cylindrical nut sections I5 and I8 integral with threaded stems I1and i8 respectively, as shown in Fig. '7. The threaded stem l'i isaxially shiftably mounted in aligned apertures 83 and 84 formed inspaced flanges 8I and 82, respectively which extend upwardly from andare formed integral with the base plate I8 of the carriage I1. Thethreaded stem 18 is axially shiftably mounted in aligned apertures I9and formed in spaced flanges and 8'6 formed integral with and extendingupwardly from the base plate I8 of the carriage I'I. Threaded on. thestems TI and I8 are adjusting nut elements 81 and 88 having handleelements 89 and 90, respectively which are receivable in notches 9I and92 formed in the vertical flange I9 of the carriage H. The stems IT and1'8 have threads 93 and 94, respectively of opposite pitch which is sopredetermined as to separate the nut sections 15 and 18 sufficiently todisengage their threads from the screw member 68 when the nut elements81 and 88 are rotated substantially one half turn relative to thethreaded stems I1 and I8, respectively. When the handles 89 and are inthe position shown in Figs. 4 and 5, the nut sections 15 and I6 are inthreaded engagement with the screw member 68 and turning of the screwmember in opposite directions shifts the carriage I1, and lower end ofthe boom member 29 which the carriage supports, longitudinally of thetrack toward and away from the lower ends of the links 45, respectively.When the handles 89 and 98 of the hoisting units A and B are in thepositions shown in Figs. 1, 4 and 5 the boom member 29 of both hoistingunits are simultaneously moved upwardly or downwardly depending upon thedirection of rotation of the screw member 68. The handles 89 and 90associated with both or either one of the hoisting units may be turnedin a clockwise direction substantially 189 from the positions shown inFigs. 1, 4 and 5 to disengage the threads of the respective nut sections15 and Hi from the threads of the screw 68, thereby permitting rotationof the screw 68 to shift the lower end of only one or the other of theboom members 29, or permitting rotation of the screw 68 without shiftingeither of the boom members 29, as desired.

The cooperating threads of the screw member 68 and nut sections 15 and16 have an irreversible pitch and therefore while rotation of the screwpositively drives the boom members 29 upwardly and downwardly, theweight of an elevated load supported on the boom member can not rotatethe screw member 68. Accordingly the threaded engagement between thescrew member 68 and the nut sections 15 and I6 serves as a lock topositively hold each boom member it in any selected position to which itis shifted by rotation of the screw member.

The screw member 68 is preferably driven through suitable reduction gearmechanism, generally designated by the numeral 95, which is in turndriven by a reversible electric motor The gear mechanism comprises ahousing l2i1, having an opening I2I in its left end wall for receiving ashaft I22 which has a coupling 23 attached to the screw member 68, asshown in Fig. 10. The shaft 122 is journalled in bearings I24 and I25which rotatably support it and resist thrust of it in both directions.The shaft 622 has a bevel gear 123 on its inner end which is meshed witha bevel gear I21 fixed to the end of a vertical shaft I28 which isjournalled in bearings I30 and I8I mounted in the upper and lower wallsof the housing I20, respectively. A large bevel gear I29 mounted on theshaft I28 is meshed with a bevel pinion I30 on the shaft I3I of themotor 96. The motor shaft I3I is journalled .in ,a bearing {I 32 which,is :mounted in the end wall ,of the housing .I 20.

The bevel gears :and pinion are predetermined :in size to produce adesired vgear reduction, the final drive of which .is presented ,by .theshaft I22 at .a low level which accommodates .low ,positioning of thescrew member 68 which ,itdrives.

The .electric motor 96 .is provided with a .control circuit, the wire.diagram of :which is schematically shown in 9.. The control circuitincludes a portable switch unit -91, preferably having two push buttonswitch elements '98 .and 99 of conventional construction which establishforward and reverse,drivingcircuitsof themotor .96. The switch elements98 and 9,9 are preferably of the type which are spring urged to openpositions and which have to be .manually held in closed positions. Theswitch unit 91 is connected onthe-endof a long cable I06 which .can beextended -.to positions adjacent the hoisting units A .and B tofacilitate control by an attendant while standing close to either unit.The cable lfiflincludesthree wires I9I, I02 and I03. The center wire Inis connected to one terminal of each of the switch elements .98 and .69and the wire .-.IIII is-connected only to the switch element!!!) and thewire I03 isconneoted only to the switch element 9.8. Depression of theswitch element 99 produces forward drive of the motor :96 .forraisingthe booms 29 and depression of :the :switchclement 98 produces reversedrive .of the :motor66 for lowering the boom elements.

Connected inseries in .the wire I03 is a conventional limit switch I04shown in Figs 1 and 9 which is mounted onthe rail IQ and has a.rightwardly-spring urged plunger I which is engageable by'the carriageI! of the hoisting unit A when the carriage I'I reaches its extremeleftward position corresponding to the lower .position of the boom-,member 29. Opening of the limit switch IIi Lthus terminates thedownward drive of screw 68. A limit switch I06 having a leftwardlyspring urged plunger I01 is mounted onthe rail III at a location on theright of the boom member .29, as viewed in-Fig. 1. limit switch I66isconnected in series in the wire IIII and serves tov open the forwarddriving .circuit of the motoriB when the boom member 29 reaches apredetermined upper position. It should be notedthat while the limitswitches I04 and. I06 areshown associated only with the hoisting unit Awhich is fixed in position, similar limit switches. may be applied tothe hoisting unit 15. However, ony one set of limit switches is requiredto safeguard each hoisting unit against excessive strain by urging ofits boom member beyond either the'limiting upper or limiting lowerpositions thereof.

In operation of the hoisting apparatus in lifting a vehicle, thevehicleisdriven over the base structure including the rails I0 andIIwhile the hoisting units are fully lowered-and-substantially completelynested between the rails -III and II with all but the load-receivingseats and 36' and insignificant portionsof theplates 46 andlevers45;disposed-below the plane-of the upper extremities -of therails. The wheels'of the vehiclemay be supported by the floor in whichthe base structure is submerged or if .a platform is employed, then thewheels of the vehicle are supported .on theplatform I6in which the railsII) and II..a-re-submerged, as, shown in 2. ...In either. case, ,d epressions .I 09 are formed ;ad.iacent.the basestructure, in-either flooror the CPI '4 The center II2 carried by a block platform for receivingthe rear wheels, for example, to position the rear axle of the vehiclein registering alignment with the seat 36 of the hoisting unit A so asto be engaged thereby when the boom member 29 is initially raised. The

,seat 316' of the hoisting unit B may be positioned to engage suitablestructure at the front end portion of the'vehicle by disengaging thethreads of the nut sections I5 and I6 from the thread of the screw 68 byoperation of the handles 89 and 9 9 and thereafter the pinion segments56 may be lifted out-of engagement with the racks .65 by lifting uponthe handle 61. With the parts of the hoisting unit B in the abovedescribed condition, the hoisting unit may be manually shifted in eitherdirection to properly position its seat 35 where desired. When thehoisting unit Bis thus adjustably positioned, the nut sections I5 and 16may be reengaged with the screw 68 and the pinion segments 66 may be re-;engaged with the rack 65 to condition the hoisting unit B foroperation.

The hoisting unit B may be mechanically shifted after the pinionsegments 66 have been lifted from the rack 65, by allowing the nutsections -I5 and I6 to remain engaged with the screw 68 and disengagingthe nut sections of the hoisting unit A from the screw. Ro-

tation of the screw 58 in opposite directions by bers are in their lowerpositions.

The seats :36 and 35' may be preset in position in advance-of driving ofa vehicle over the hoisting apparatus with the aid of a tool shown inFig. 11. This tool comprises a bar IIII having a fixed center III at oneend and a shiftable H3 shiftably mounted on the opposite-end. portion ofthe bar. The block II3 may be set by a screw H4 in an adjusted portiondetermined by applying the tool to thecenters of the hub caps of avehicle or other structure thereof with which the seats 36 and 36 aredesired to register, or the bar IIO may be provided with suitablemarking (not shown) designating the proper positions of the shiftablecenter H2 for various makes and types of vehicles. When the centers IIIand I I2 are so located, one thereof may be placed in line with thenotch of the seat ,35 of the hoisting unit A and the hoisting unit B maybe shifted until the notch of its seat 36' is aligned with the othercenter.

When the vehicle is positioned relative to the hoisting units as abovedescribed and the forward drive control switch element 99 is depressed,the

.screwmember 68 is so rotated as to urge the carriages I! of both unitsrightwardly as viewed in Fig. 1. This action shifts the boom members 29simultaneously upwardly, the movement of the seats 36 and 36 being socontrolled, as illustrated in Fig. 3, by the links 45 as to confine eachseat movement to a course which does not depart significantly from avertical course.

The location of the pivots 41 of each unit above the plane defined bythe pivotal axis of the lower endsof the links 45 and the pivotal axisof the .boom member thereof, prevents unintended locking of theboommember 29 and links 45 ,in an alignedrelationship and additionallyprovides a greater mechanical advantage during initial lifting of theload. Since the minimum mechanical advantage in the leverage systemembodied in the above described hoisting apparatus occurs when theapparatus is fully contracted, increasing of the mechanical advantage atthis end of its range of movement significantly reduces the maximumpower requirements and size of the motor 96.

Lowering of the boom members 29 is accordingly produced by depression ofthe switch element 98 which causes reverse rotation of the screw 68.

Either one of the hoisting units A and B may be selectively renderedinoperative by disengaging its nut segments 15 and Hi from the screwmember 68 so as to elevate only the boom member 29 of the other unit. Inall instances of operation of the apparatus the boom members arepositively driven upwardly and downwardly by the screw.

Although but one specific embodiment of the invention is herein shownand described, it will be understood that various changes in the detailsand construction thereof may be made without departing from the spiritand scope of my invention.

I claim:

1. Hoisting apparatus including a base structure, a pair of hoistingunits mounted on said base structure each comprising a boom member andan operating lever pivotally attached at one end to an intermediateportion of each boom member respectively, one of said hoisting unitsbeing shiftable longitudinally of said base structure, means coactingwith the other end of the lever of said latter hoisting unit for holdingsaid latter hoisting unit against said shifting move- .ment, meansmounting each of said boom members on one of said hoisting unitsrespectively for shifting movement between generally horizontal andgenerally vertical positions, a common driving member for positivelypropelling each of said boom members from each of said positions to theother position, and mechanism for releasably effectively coupling eachof said boom members independently to said common driving member, saidshiftable hoisting unit being movable longitudinally of said basestructure without affecting :said other unit by operation of said commondriving means when said shiftable hoisting unit is coupled with saiddriving member and said holdting means is released and the boom memberof the other hoisting unit is uncoupled from said common driving means,and apparatus for selectively operating said common driving member inrespectively opposite directions.

2. Hoisting apparatus including a base structure, first and secondhoisting units mounted on said base structure each comprising a boommember having a load receiving seat on one end, said second hoistingunit being shiftable longitudinally of said base structure, meansmounting each of said boom members for shifting movement betweengenerally horizontal and generally vertical positions including a leverelement pivotally attached at one end to each boom member respectively,means pivotally fixing the other end of the lever element of said firsthoisting unit to said base structure, detachable cooperating means onthe other end of the lever element of said second hoisting unit and onsaid base structure respecstructure,a common driving member forpositively driving each of said boom members from each of said positionsto the other position, mechanism for releasably efiectively coupling theend of each boom member opposite its load receiving seat with saidcommon driving member, said second hoisting unit being movablelongitudinally of said base structure by operation of said commondriving means when said cooperating means are detached and the boommember of said second hoisting unit is coupled with said common drivingmember, and apparatus for selectively operating said common drivingmember in respectively opposite directions.

3. Hoisting apparatus including a base structure comprising a track, ahoisting unit shiftably mounted on said track including a boom memberhaving a load receiving seat on its upper end portion, means holding thelower end of said boom member against vertical displacement relative tosaid track and pivotally and shiftably supporting said boom member formovement longitudinally of said track, a, lever element pivotallyattached at one end to an intermediate portion of said boom member forguiding it in its movement between said positions, releasablecooperating holding means on the other end of said lever element and onsaid base structure respectively for supporting the latter end of saidlever element for pivotal movement relative to said base structure at aplurality of selected positions along said base structure, and a drivingmember operatively threadedly connected with the lower end portion ofsaid boom member for shifting said lower end portion longitudinally ofsaid track to raise and lower said load receiving seat, said hoistingunit being movable longitudinally of said base structure by operation ofsaid driving member when said cooperating holding means are released.

4. Hoisting apparatus including a stationary base structure, a hoistingunit bodily shiftably mounted on said base structure comprising a boommember, means for releasably holding said hoisting unit against bodilyshifting movement, means mounting said boom member on said hoisting unitfor shifting movement between generally horizontal and generallyvertical positions, a driving member extending longitudinally of andoperatively mounted on said base structure in fixed location relativethereto, and means connecting said driving member with said boom memberfor positively propelling the latter from each of said positions to theother position, said hoisting unit being shiftable longitudinally ofsaid base structure by operation of said driving member when saidholding means is released.

5. Vehicle hoisting apparatus including a pair of hoisting units eachhaving a rigid fixed length boom member, means mounting the boom memberof each hoisting unit for shifting movement in the same directionbetween lower and upper positions, separate vehicle engaging members onthe respective boom members of said units, a common driving member forpositively propelling said boom members from each to the other of saidpositions comprising a rotatable screw element having threads of thesame direction associated with each of said boom members, a nut elementon each of said boom members in threaded engagement with said screw,said nut and screw elements having threads of irreversible pitch foreffectively locking said boom elements in all positions in their pathsof movement, and apparatus for selectively propelling said screw elementin respectively opposite directions.

6. Hoisting apparatus comprising a base structure including spaced railshaving a groove therebetween, a pair of hoisting units each having aboom member receivable substantially completely in said groove when inits lower position, means mounting each boom member for shiftingmovement between upper and lower positions, means for translativelyshiftably supporting said units on said rails for movementlongitudinally of said rails, said boom member mounting means and saidunit supporting means being substantially completely receivable in saidgroove, and a common driving member in said groove connected with eachboom member for positively driving them upwardly and downwardly.

7. Hoisting apparatus comprising a base structure, a hoisting unit,means bodily shiftably mounting said hoisting unit for movementlongitudinally of said base structure including a carriage shiftablymounted on said base structure, said hoisting unit including a boommember shiftably mounted on said carriage for movement between generallyhorizontal and generally vertical positions, and mechanism forselectively bodily shifting said hoisting unit relative to said basestructure and for positively selectively shifting said boom structuretoward its generally horizontal and generally vertical positionsrespectively comprising a rotatable screw element on said base structureand a nut element in threaded engagement with said screw element andattached to said carriage.

8. Hoisting apparatus comprising a base structure, a hoisting unit,means bodily shiftably mounting said hoisting unit for movementlongitudinally of said base structure including a carriage shiftablymounted on said base structure, said hoisting unit including a boommember having its lower end portion pivotally mounted on said carriagefor movement between generally horizontal and generally verticalpositions, mechanism for selectively bodily shifting said hoisting unitrelative to said base structure and for positively selectively shiftingsaid boom structure toward its generally horizontal and generallyvertical positions respectively comprising a rotatable screw element onsaid base structure and a nut element on said carriage and adapted forreleasable threaded engagement with said screw element, means forreleasably holding said nut element in threaded engagement with saidscrew element and means for releasably holding said hoisting unitagainst shifting bodily relative to said base structure.

9. Hoisting apparatus comprising a base structure, a hoisting unit,means bodily shiftably mounting said hoisting unit for movementlongitudinally of said base structure including a carriage shiftablymounted on said base structure, said hoisting unit including a boommember having an end portion shiftably mounted on said carriage formovement between generally horizontal and generally vertical positions,a rotatable screw element journalled on said base structure, a nutelement in threaded engagement with said screw element, means holdingsaid nut element against rotation with said screw element andoperatively connecting it with said carriage for shifting said hoistingunit bodily linearly of said base structure and shifting said boommember toward its generally vertical and generally horizontal positionsrespectively in response to rotation of said screw element inrespectively opposite directions, and reversable driving mechanism forselectively driving said screw element in respectively oppositedirections.

10. Hoisting apparatus comprising a base structure, a hoisting unit,means shiftably mounting said hoisting unit for bodily movement relativeto said base structure comprising a support means shiftably mounted onsaid base structure, said hoisting unit including a boom member havingits lower end portion pivotally mounted on said support means formovement between generally horizontal and generally vertical positions,a rotatable screw element journalled on said base structure, a nutelement comprising relatively shiftable sections adapted to bereleasably engaged with said screw element, means for releasably holdingsaid sections of said nut element in threaded engagement with said screwelement, means operatively connecting said nut element with said supportmeans and for holding it against rotation with said screw and againstrotation with respect to said support means for shifting said hoistingunit bodily relative to said base structure and for shifting said boommember toward its generally vertical and generally horizontal positionsrespectively in response to rotation of said screw element inrespectively opposite directions, and reversible drive mechanism forselectively driving said screw element in respectively oppositedirections.

11. Hoisting apparatus comprising a base structure including ahorizontal track member, a hoisting unit, means shiftably mounting saidhoisting unit for bodily movement relative to said base structureincluding a carriage shiftably mounted on said track member having meanscoacting therewith for holding said carriage against movementtransversely and vertically of said track member, said hoisting unitincluding a boom member pivotally mounted at one end on said carriagefor shifting movement from a position substantially parallel to saidtrack member to a substantially vertical position, a lever memberpivotally mounted at one end for pivotal movement relative to said basestructure and pivotally attached at its opposite end to said boom memberat a location intermediate the ends of said boom member, a rotatablescrew element journalled in and extending substantially parallel to saidbase structure, a nut element on said carriage in threaded engagementwith said screw element for selectively shifting said hoisting unitbodily relative to said base structure and for shifting said carriagetoward and away from said first mentioned pivoted end of said lever forrespectively raising and lowering said boom member, and mechanism forselectively rotating said screw member in respectively oppositedirections.

12. Hoisting apparatus including a stationary base structure, a hoistingunit bodily shiftably mounted on said base structure comprising a boommember, means for releasably holding said hoisting unit against bodilyshifting movement, means mounting said boom member on said hoisting unitfor shifting movement between generally horizontal and generallyvertical positions, a driving member extending longitudinally of andoperatively mounted on said base structure in fixed location relativethereto comprising a screw element journalled on said stationary basestructure and a nut threaded on said screw element and attached to saidboom member, and means connecting said driving member with said boommember for positively propelling the latter from each of said positionsto the other position, said hoisting unit being shiftable longitudinallyof said base structure by operation of said driving member when saidholding means is released.

DAVID A. WALLACE.

References Cited in the file of this patent Number UNITED STATES PATENTSName Date Prouty Feb. 19, 1907 Feix Mar. 15, 1910 10 Price June 14, 1921Seldomridge Aug. 20, 1929 Martin Feb. 12, 1935 Weaver Sept. 24, 1935Dement June 9, 1936 15 Number Number Name Date Meacham July 2, 1940Weaver Dec. 12, 1950 Wallace Nov. 27, 1951 Wallace Nov. 27, 1951 WallaceNov. 27, 1951 Wallace May 27, 1952 Wallace May 27, 1952 FOREIGN PATENTSCountry Date Italy June 23, 1932 Great Britain Jan. 29, 1931 GreatBritain May 27, 1935

